He was born on February 12, 1867 in Washington D.C. to Henry Caleb Spencer Sr. and Sarah Jane Andrews. He had two younger siblings, Platt Rasson Spencer, who died in infancy, and Henry "Harry" Caleb Spencer Jr., who was also an early recording artist. Before entering the phonograph industry, he worked as an instructor for the Spencerian Business College in Washington. He began recording for the Columbia Phonograph Company, in 1889 or 1890.^[2] Between 1892 and 1897 he recorded extensively for the New Jersey Phonograph Company and its successor the United States Phonograph Company.^[3] He specialized in vaudeville sketches and comic songs, but also sang sentimental ballads popular at the time.^[3] He returned to Columbia in 1898 for an exclusive contract^[4] then began recording for Berliner Gramophone (disc) records in 1899 and continued with Victor and Columbia as discs became the dominant format in the early 1900s.^[5]

He began performing with banjoist Vess L. Ossman in 1901 and with Ada Jones in 1905. He is best remembered today for his vaudeville-style comic sketches, such as "The Arkansaw Traveler" (1902), combining clever turns of phrase, ironic elocutionary delivery, sound effects and music to create colorful dialogues featuring itinerant Southerners, auctioneers, circus barkers, and Irish, Jewish or Black Americans.^[6] Many of his roles were performed in either blackface or brownface. Spencer's output was eclectic. He imitated animal sounds in "A Barnyard Serenade" (1906) and released another record titled "The Transformation Scene from 'Dr. Jekyll and Mr. Hyde'," but also popularized songs still known today such as "Ta-Ra-Ra-Boom De-ay" and "A Hot Time in the Old Town." Music historian Bob Stanley deems it "probable" that Spencer's comedic "Arkansaw Traveler" routine was the first record to sell one million copies, though official documentation is lacking.^[7]

Spencer was married twice. He married Margaret Allen in 1885 and remained married until her death in 1891 in which he had two daughters, one who was stillborn and Sara Allen Spencer. He married Elizabeth Norris in 1892 in which he had three more daughters, Myrtle Lincoln Spencer, Ethel Leonora Spencer and Clara Barton Spencer.

As the popularity of Len's style of humor waned in the latter part of the decade, he opened a booking agency called "Len Spencer's Lyceum" in New York.^[8] He died of a cerebral hemorrhage or heart attack while working at the Lyceum on December 15, 1914, at age 47.^[9] His funeral was held at the Frank E. Campbell Funeral Chapel and his remains were cremated and buried in Glenwood Cemetery.^[10]

Some of his most popular recordings include:

• "Ta-Ra-Ra-Boom De-ay" (1892)
• "The Old Folks at Home" (1892)
• "Little Alabama Coon" (1895)
• "Dat New Bully" (1895)
• "A Hot Time in the Old Town" (1897)
• "Hello! Ma Baby" (1899)
• "Ma Tiger Lily" (1900)
• "Arkansaw Traveler" (1902)
• "Peaches and Cream", (1906) with Ada Jones (John B. Lowitz wax cylinder)^[8]

• Ada Jones

• Works by Len Spencer at Project Gutenberg
• Works by or about Len Spencer at Internet Archive
• Len Spencer cylinder recordings, from the Cylinder Audio Archive at the University of California, Santa Barbara Library.
• Len Spencer recordings at the Discography of American Historical Recordings.
• A 1947 biography of Spencer in Jim Walsh's "Favorite Pioneer Recording Artists", and a 1958 update with corrections.